Dietary glucose in excess is stored in the liver in the form of glycogen. As opposed to direct conversion of glucose into glycogen, the hypothesis of the postprandial lactate shuttle (PLS) proposes that dietary glucose uptake is metabolized to lactate in the gut, thereby being transferred to the liver for glycogen storage. In the present study, we provide evidence of a PLS in young healthy men and women. Overnight fasted participants underwent an oral glucose tolerance test, and arterialized lactate concentration and rate of appearance were determined. The concentration of lactate in the blood rose before the concentration of glucose, thus providing evidence of an enteric PLS. Secondary increments in the concentration of lactate in the blood and its rate of appearance coincided with those of glucose, which indicates the presence of a larger, secondary, systemic PLS phase driven by hepatic glucose release. The present study challenges the notion that lactate production is the result of hypoxia in skeletal muscles, because our work indicates that glycolysis proceeds to lactate in fully aerobic tissues and dietary carbohydrate is processed via lactate shuttling. Our study proposes that, in humans, lactate is a major vehicle for carbohydrate carbon distribution and metabolism.

过量的膳食葡萄糖以糖原的形式储存在肝脏中。与葡萄糖直接转化为糖原相反，餐后乳酸穿梭（PLS）假说提出，饮食中的葡萄糖摄取在肠道中代谢为乳酸，从而转移到肝脏进行糖原储存。在本研究中，我们提供了年轻健康男性和女性 PLS 的证据。禁食过夜的参与者接受了口服葡萄糖耐量测试，并测定了动脉乳酸浓度和出现率。血液中乳酸浓度先于葡萄糖浓度上升，从而提供了肠道 PLS 的证据。血液中乳酸浓度及其出现率的二次增量与葡萄糖的增量一致，这表明存在由肝葡萄糖释放驱动的更大的、二次的、全身性PLS相。本研究挑战了乳酸的产生是骨骼肌缺氧的结果的观点，因为我们的工作表明，糖酵解在完全有氧的组织中进行为乳酸，并且膳食碳水化合物通过乳酸穿梭进行加工。我们的研究表明，在人类中，乳酸是碳水化合物碳分布和代谢的主要载体。